Transparent Impact Resistant System

ABSTRACT

A transparent impact resistant system, that includes a sheet of aluminum oxynitride, a sheet of single-crystal aluminum oxide and an interlayer attached between the aluminum oxynitride and the single-crystal aluminum oxide. Additional sheets of each material can be added depending on the threat level. The interlayer may include an energy absorption layer and a reinforcement layer.

FIELD OF THE INVENTION

The field of invention related to armor systems and, more particular to bullet-proof windows.

BACKGROUND

This purpose of this invention is to produce a new and improved transparent impact resistant system (TIRS) which is tailored primarily for bullet-proof windows or other impact resistant applications. Traditional bullet-proof window panes are of large areal densities that can defeat mainly small to medium caliber bullets. Larger caliber bullets require traditional bullet-proof window pane thicknesses of the order of 10.2 to 12.7 cm (4.0 to 5.0 in.).

Ballistic glass sections are typically laminated glass panels interconnected with Bucalite, polyvinyl butyral (PVB), interlayers. The distribution, arrangement, individual laminae thicknesses, and overall section thickness dictate the performance of the sections against various Underwriters Laboratory UL-752 (UL-752) defined ballistic levels. These levels range from small caliber bullets, such as the 9 mm (Level I) threat, to large caliber, such as M-14 or M-16 multiple bullets (corresponding to Levels VII and VIII, respectively), as well as the .50 caliber (Level X). The state-of-the-art of such a window section incorporates a combination of improved glass plies of various strengths, connected using transparent interlayers, such as polyvinyl butyral (PVB) or Ionoplast (IonP). The glass plies can also be of variable thermal characteristics, depending on their environmental application.

There are several problems associated with the traditional bullet-proof windows. The main problem is the actual size of the composite pane that is required to arrest a high kinetic energy (K.E.), high momentum ammunition, such as the 7.62-mm or, even worse, the .50 caliber. The brittle nature of the silicon oxide based glass section and the poor absorption and distribution of the initial energy of the impacting entity, because of development of “infinite stresses” in the vicinity of its tip, makes the typical bulletproof glass impractical for applications requiring defeat of .50 caliber ammunition due to weight restrictions.

In addition, the use of several layers of glass (anywhere from twelve to eighteen) in conjunction with the use of IonP interlayers result in a section that is not clear and, consequently, the term transparent loses its true sense.

Variations of the bullet-proof window panes may also use single crystal layers of spinels or aluminum oxinitride ((AlN)_(x.)(Al₂O₃)_(1-x), where 0.30<x<0.38), also known as ALON, placed externally, on the side of impact, fused to one or more internal glass layers via PVB, and terminating with a polycarbonate layer on the side opposite from the impacting surface.

Both variations of bullet-proof glass, described above, may resist the full penetration of the 7.62 mm, the medium size ammunition, but they still require significant thickness to defeat the .50 caliber threat.

SUMMARY

A transparent impact resistant system (TIRS) may be used as an improved practical, transparent, bullet-proof composite section using newly developed and already field tested materials. The combination of these materials into a new composite section results in a (TIRS) that is, at the most, 51 mm (2.0 in.) and it can defeat a .50-caliber, 48.6 g (750 grains) average mass* bullet from a standoff of 4.57 m (15 ft). The new bullet-proof system can be modified to resist the full penetration of a .50 caliber bullet with as little as 3.5 to 5.1 cm (1.4 to 2.0 in.). The TIRS also has more general applications to produce impact resistant materials. *The mass of the .50 caliber ammunition can vary by as much as 10 g (155 grains)

In one general aspect, a transparent impact resistant system includes aluminum oxynitride, single-crystal aluminum oxide, and at least one interlayer attached between the at least one sheet of aluminum oxynitride and the at least one sheet of single-crystal aluminum oxide.

Embodiments may include one or more of the following features. For example, the interlayer may have an energy absorption layer, a reinforcement layer and/or a waveguide.

The waveguide may be a single sheet of aluminum oxinitride, single sheet of single-crystal aluminum oxide or another type of spinel element. The energy absorption layer may be polyvinyl butyral, a polymer or an ionoplast layer.

In one of the embodiments, the aluminum oxynitride is positioned on the side of a potential impact relative to the single-crystal aluminum oxide.

In another general aspect, a transparent impact resistant system includes a first rigid layer, a second rigid layer, and at least one interlayer attached between the first rigid layer and the second rigid layer. The interlayer may have an energy absorption layer and a waveguide.

The waveguide may be a spinel element such as a single sheet of aluminum oxynitride or a single sheet of single-crystal aluminum oxide. The energy absorption layer may include polyvinyl butyral or a polymer.

The first rigid layer may be a sheet of aluminum oxynitride positioned on a side of a potential impact. The second rigid layer may be a sheet of single-crystal aluminum oxide.

In still another general aspect, a transparent impact resistant system includes a first rigid layer, a second rigid layer, and an interlayer attached between the first rigid layer and the second rigid layer. The interlayer has an energy absorption layer and a reinforcement layer and may also include one or more of the above features.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a and 1 b—Impact Tests for Configuration “B”, Vo=4.03 km/s, D=6.35 mm 1 a) Initial Setup and 1 b) Late Time Response.

FIG. 2—Graph of Kinetic Energy vs. Time Variation for Configuration “B” with Vo=4.03 km/s and D=6.35 mm.

FIGS. 3 a and 3 b—Impact Tests for Configuration “B”, Vo=3.90 km/s, D=3.97 mm 3 a) Initial Setup and 3 b) Late Time Response.

FIGS. 4 a and 4 b Graphs of 4 a) Projectile's C. G. Position and 4 b) K.E. vs. Time Variation for Configuration “B” with Vo=3.90 km/s and D=3.97 mm.

FIG. 5—Impact Test of Late Time Response for Configuration “C”, Vo=2.67 km/s, D=6.35 mm.

FIG. 6—Graph of Projectile's K.E. vs. Time Variation for Configuration “C” with Vo=2.67 km/s and D=6.35 mm.

FIGS. 7 a and 7 b—Graphs of Projectile's C.G.'s a) Position and b) Velocity vs. Time Variation for Configuration “C” with Vo=2.67 km/s and D=6.35 mm.

FIG. 8—Impact Test of Late Time Response for Configuration “C”, Vo=2.90 km/s, D=3.97 mm.

FIG. 9—Graph of Projectile's K.E. vs. Time Variation for Configuration “C” with Vo=2.90 km/s and D=3.97 mm.

FIGS. 10 a-10 d—Tests of Six-Ply Arrangement Subjected to 7.62-mm Impacting Projectile, V₀ of 875 m/s, for Estimating V₅₀ 10 a) Original Configuration, 10 b) Late Time Response, 10 c) K.E. Degradation, and 10 d) Penetrator's Select Velocity Response Along Points on its Axis of Symmetry.

FIGS. 11 a-11 d—Tests for Three-Ply Arrangement for Estimating V₅₀ 11 a) Original Configuration, 11 b) Late Time Response, 11 c) K.E. Degradation, and 11 d) Penetrator's Select Position Along Axis of Symmetry Velocity Response subjected to the 7.62-mm impacting projectile with V₀ of 791 m/s.

FIG. 12—Close-up of Numerical Model (Slice through the Vertical Axis).

FIG. 13—7.62-mm Slug Select Station Position Variation with Time.

FIG. 14—Resting Position of the 7.62-mm Ammunition Slug.

FIGS. 15 a and 15 b—Final Configuration and Penetration Levels of the 7.62-mm Slug Impacting 23-mm (15 a) and 33-mm (15 b) TIRS Sections, respectively.

FIG. 16—Numerical Setup of the .50 Caliber Example 2 Case.

FIGS. 17 a and 17 b—Final Configuration and Penetration Levels (17 a) and Select Bullet Station Position Variation with Time (17 b) for the .50 Caliber Impacting a 40.5-mm TIRS Section.

FIGS. 18 a-18 d—18 a) Initial (t=0) and 18 b) Rest (t>240 ms) Configurations, Select Bullet Station 18 c) Position, and 18 d) Velocity Variation with Time for the 46 g, .50 Caliber Impacting a 42.0-mm Section.

FIGS. 19 a-19 d—19 a) Rest (t>260 ms) Configuration, 19 b) Select Bullet Station Velocity Variation with Time, 19 c) Kinetic Energy Dissipation of Ammunition, and 19 d) Select Bullet Position Variation with Time for the 52 g, .50 Caliber Impacting a 42.0-mm TIRS Section.

FIGS. 20 a-20 d—20 a) Initial and 20 b) Final Configurations, 20 c) Select Bullet Station Velocity Histories, and 20 d) Kinetic Energy Dissipation of Ammunition for the Upper Bound UL-752, Level IX.

FIGS. 21 a-21 d—21 a) Initial and 21 b) Final Configurations, 21 c) Select Bullet Station Velocity Histories, and 21 d) Kinetic Energy Dissipation of Ammunition for the Upper Bound UL-752, Level X.

DETAILED DESCRIPTION

The overall approach was differentiated into four tasks:

-   -   1. Collect already existing experimental data that report the         behavior of laminated glass units (LGU's) under various impact         environments. These include medium caliber ammunition, such as         the 7.62-mm ballistic, impacting multilayered LGU's;     -   2. Conduct numerical simulations using explicit finite element         analysis (FEA) codes, such as the free licensed software         FreeFEM++, in order to compare the experimental with the         numerical data;     -   3. Calibrate the numerical models to match the experimental         results in the event that gross differences exist between the         two; and     -   4. Once the numerical work is completed, employ FEA techniques         to simulate new TIRS sections using combinations of ALON,         sapphire (Al₂O₃), IonP, polycarbonate, and/or a sheet of         alkali-aluminosilicate glass (AAL) as the materials under         consideration.

Task 1: Collection of Already Existing Experimental Data.

Two sets of data were collected from the open literature. The reference for the first set of data is:

-   Ha, Y, Guang, G, Chi, R., Pang, B., “Experimental and Numerical     Studies of Laminated Glass Subject to Hypervelocity Impact,” Journal     of Explosion and Shock Waves, May, 2005.

A total of seventeen impact tests were presented in this paper. Of these, only nine employed three distinct plies of glass comprising the LGU's. The other eight tests were impacts on either stacks of glass plies with no interlayer connection or they involved more than three plies. Moreover, some of the experimental setups were duplicates to ensure repeatability of the results. The remaining experimental setups involved two different configurations of LGU's. One setup uses three 12-mm glass plies that are connected using 2×0.76-mm PVB interlayers. This arrangement is referred to a configuration “B”. A second setup, uses a 12-mm glass ply sandwiched between two 5-mm glass plies. All plies are interconnected using two 0.76-mm PVB interlayers. This arrangement is referred to as configuration “C”. In addition, two different size of impacting entities were used, a 6.35-mm and a 3.97-mm spherical ball made of 2017-T4 aluminum alloy.

Four representative experimental setups were chosen to be numerically simulated, namely:

-   -   1. Configuration “B” with an initial impact velocity of 4.03         km/s, using the 6.35-mm diameter spherical impactor.     -   2. Configuration “B” with an initial impact velocity of 3.90         km/s, using the 3.97-mm diameter spherical impactor.     -   3. Configuration “C” with an initial impact velocity of 2.67         km/s, using the 6.35-mm diameter spherical impactor.     -   4. Configuration “C” with an initial impact velocity of 2.90         km/s, using the 3.97-mm diameter spherical impactor.

All simulated setups assume normal impact of the projectile onto the target.

The second set of experimental data gathered from the open literature is from the following reference:

-   Richards, M., Clegg, R., and Howlett, S. “Ballistic Performance     Assessment of Glass Laminates Through Experimental and Numerical     Investigation,” The 18th International Symposium and Exhibition on     Ballistics San Antonio, Tex., 1999.

Three experiments were reported in this reference. All of the experiments used the 7.62 mm×51 mm NATO ball round as the standard projectile. The first experiment incorporated a monolithic glass panel. The second section was a LGU's made of three, 6-mm glass plies which were interconnected via polyurethane interlayers. The third section's makeup consisted of six, 3-mm glass plies also interconnected using polyurethane interlayers. All three assemblies were attached to a 6-mm polycarbonate backing material. The ballistic limits, V₅₀̂, values were reported in each case. ̂The V₅₀ ballistic limit is equivalent to a 50% probability of the projectile penetrating the target.

Two experimental setups were chosen to be numerically simulated from this set of experiments, namely:

-   -   1. The six, 3-mm LGU subjected to the 7.62-mm impacting         projectile with an initial velocity of 875 m/s.     -   2. The three, 6-mm LGU subjected to the 7.62-mm impacting         projectile with an initial velocity of 790 m/s.

Both experimental and the numerical setups assume normal impact of the projectile with respect to the target.

Task 2: Numerical Simulations Using Explicit Codes. Comparison of Experimental Results With Numerical Output.

The paper by Ha et al. provides detailed description of the LGU's constituent materials and their mechanical properties. The numerical models, built herewith, used the constitutive material parameters provided by the authors. Explicit modeling of the spherical projectile and the LGU's was carried out.

Configuration “B”, Velocity=3.9 km/s, with 3.97-mm Diameter Spherical Projectile

FIGS. 1 a and 1 b show the 2-D representation of the FEA model. Each of the material components was numerically represented. The overall thickness of the section (target) is 37.56 mm. The spherical projectile was assigned the hypervelocity value of 3.9 km/s.

As shown in FIG. 2 the projectile is converted into a slug and a total penetration of slightly less than 10 mm is achieved. This value is in close agreement with that provided by the experimental outcome, which was reported as being 9.8 mm.

The majority of the K.E. of the projectile dissipates within the first 0.01 ms (FIGS. 3 a and 3 b) and reaches zero within the first 0.025 ms.

Configuration “B” with an Initial Impact Velocity of 4.04 km/s, Using the 6.35-mm Diameter Spherical Impactor.

The 37.56-mm section is subjected to 4.04 km/s impact of a 6.35-mm diameter sphere. The initial and late time response of the arrangement are shown in FIGS. 3 a and 3 b, respectively. A trace at the center of gravity (c.g.) of the impacting sphere reveals the degradation of the initial velocity—see FIG. 4 a—until it completely disappears. The K.E. dissipation plot is also provided in FIG. 4 b. It is notable that despite the fact that the initial K.E. of this experiment is substantially less than that of the one reported in the previous section (the relative ratio of their K.E.'s is 7 to 30), yet the relative perforation of the two is, approximately, the same (1:1). This fact is verified both numerically and experimentally.

Configuration “C” with an Initial Impact Velocity of 2.67 km/s, Using the 6.35-mm Diameter Spherical Impactor.

The 23.56-mm thick LGU is impacted with a 6.35-mm in diameter spherical projectile, traveling at 2.67 km/s. The late time stage of the simulation is shown in FIG. 5. The K.E.'s variation of the projectile is shown in FIG. 6. It can be seen from this figure that the majority of the K.E. is dissipated within the first 7.5×10⁻³ ms. FIG. 7 a shows the relative position of the c.g. of the projectile during the course of the numerical simulation as well as that of the velocity in FIG. 7 b. The Front face perforation was reported as 8.0 mm by Ha et al. The simulated perforation is 7.98 mm.

Configuration “C” with an Initial Impact Velocity of 2.90 km/s, Using the 3.37-mm Diameter Spherical Impactor.

The late response of the 23.56-mm thick LGU subjected to the 3.37-mm diameter spherical projectile with an initial velocity of 2.90 km/s is shown in FIG. 8. The maximum perforation is restricted to within the first ply of glass (impact side) and the first interlayer for a total of 5.4 mm which is exactly the same as the experimental result reported for this particular case. FIG. 9 shows the K.E. associated with the projectile and its degradation over time.

The Six, 3-mm LGU Subjected to the 7.62-mm Impacting Projectile with am Initial Velocity of 875 m/s.

The original configuration as well as the end of the simulation response of the six-ply arrangement subjected to the 7.62-mm round with an initial velocity of 875 m/s are shown in FIGS. 10 a and 10 b, respectively. In addition, the residual K.E. and select velocities collected along the axis of symmetry of the penetrating bullet are shown in FIGS. 10 c and 10 d, respectively. The validation of the V₅₀ ballistic requirement is herewith verified since only a relatively small portion of the original K.E. is carried by the exiting slug.

The Three, 6-mm LGU Subjected to the 7.62-mm Impacting Projectile with an Initial Velocity of 790 m/s.

Similarly, the original configuration as well as the end of the simulation response for the 7-62-mm round impacting the three-ply arrangement are shown in FIGS. 11 a and 11 b, respectively. In addition, the residual K.E. and select velocities collected along the axis of symmetry of the penetrating bullet are shown in FIGS. 11( c) and (d), respectively. The validation of the V₅₀ ballistic requirement is herewith verified since only the backing material of the section is not fully compromised.

Task 3: Calibration of the Numerical Models

No calibration was deemed necessary. All numerical models predict the behavior of each of the experimental results within satisfactory limits.

Task 4: FE Techniques to Simulate New TIRS Sections Using a a Combination of ALON, Sapphire (Al₂O₃), IonP/PVB, and the AAL

Five examples are addressed to show the benefit of using ALON, sapphire, IonP, AAL, and polycarbonate layers to achieve what the typical state-of-the-art bulletproof windows can not.

Example 1

A 7.62 mm API round with an initial velocity of 793 m/s (2,600 fps), mass of 10.6 g (164 grains), impacts a composite TIRS material with alternate layers of ALON and sapphire that are connected with IonP interlayers. Five such layers (three ALON and two sapphire) are present with one of the ALON layers being exposed to impact. An additional sixth layer is made of polycarbonate and it is on the leeward (away from the impact) side of the section. The latter is fused to the third from the impacting side ALON layer with a PVB interface layer. The individual ALON, sapphire, and polycarbonate layers are each 3.0 mm thick. Each of the IonP and PVB layers is 1.5 mm thick. FIG. 12 shows a close up of the numerical setup. The black dots along the vertical axis of rotational symmetry of the bullet represent stations¹ where information is extracted concerning the final position of the slug formation. ¹ The spacing of the plotted stations is 2 mm and they are all located on the axis of symmetry. The first station is on the tip of the projectile, the second is 2 mm, the third is 4 mm, and the forth is 6 mm away from the impacting tip.

The overall thickness of the section is 27 mm, for this particular case. The degree of confidence that the ammunition will not penetrate the TIRS arrangement is 96%. FIG. 13 shows the relative compaction of the impacting 7.62 mm entity. The position versus time variations of select points¹ along the vertical axis of the bullet suggest that the slug formed penetrates 23 mm through the thickness of the TIRS (FIG. 13). It causes the bulging of the section on the side opposite from the impacting surface. The zero residual K.E. of the slug suggests that the latter is totally arrested. FIG. 14 shows the final position and formation of the slug for this particular case.

In the event that the overall thickness of the TIRS section is reduced to 23 mm consisting of 2.5-mm individual ALON, sapphire, and polycarbonate layers whilst the IonP/PVB interface layer thicknesses remain the same as before, the confidence level drops to 40%. The type of the 7.62-mm ammunition including its initial velocity, weight, angle of incidence, in-flight spin, specific makeup of the material characteristics of the bullet, affect the confidence level in defeating this level of ballistic threat. At the other extreme, if the individual layers are increased to 4.2 mm and the overall thickness of the section is 33 mm then the confidence level increases to 100%. FIGS. 15 a-15 b show a similar section slice for each of these cases as the one described for the 96% level of confidence.

Example 2

This example addresses the .50 caliber, Ball, Armor Piercing, M2 round with an initial velocity of 793 m/s (2,600 fps), weight 52 g (800 grains), impacts a composite TIRS material. The section is made, starting from the impact side and proceeding in the through-the-thickness direction, with five alternating layers of ALON (three in total) and sapphire (two in total) that are connected with IonP interlayers. The topmost layer is made of ALON. It is the first layer to be impacted by the round. A 0.75-mm PVB interlayer connects the third ALON layer to a 3-mm AAL which in turn is connected through a 0.75-mm IonP layer to three, in total, alternating ALON (2) and sapphire (1) layers. The latter are interconnected with PVB interlayers. The last ALON (most distant from the impacting side) is connected to a polycarbonate layer using an IonP interlayer. Each ALON and sapphire layer is 3.0 mm thick while each IonP, PVB, AAL, and polycarbonate layer is 1.5 mm thick.

FIG. 16 shows the numerical setup for Example 2. The black dots along the vertical axis of rotational symmetry of the bullet represent stations¹ where information is extracted concerning the final configuration of the slug formation. Additional Lagrange stations (black dots) are distributed along the thickness of the section at select locations in order to trace the velocity profile directly under the impact location.

The overall thickness of the section is 40.5 mm. The confidence is 93% that the ammunition will not penetrate the TIRS arrangement. FIGS. 17 a and 17 b show the relative compaction of the impacting .50 caliber bullet penetration (right) and the final rest position of the slug formed within the section (left).

The position versus time variation of select points along the vertical axis of the bullet suggest that the slug formed penetrates 36 mm through-the-thickness of the TIRS. It causes the bulging of the section on the opposite side from the impacting surface with the possibility of forming limited debris.

Example 3

This example addresses a similar ballistic threat as that of Example 2, namely the .50 caliber, Ball, Armor Piercing, M2 round with an initial velocity of 793 m/s (2600 fps), impacting a modified composite TIRS material. The section is comprised, starting from the impact side and proceeding in the through-the-thickness direction, of five alternating layers of ALON (three in total) and sapphire (two in total) that are connected with IonP interlayers. The topmost layer is made of ALON and it is the first layer to be impacted by the round. A 3.0-mm thick PVB interlayer connects the third ALON layer to three, in total, alternating ALON (two) and sapphire (one) layers which in turn are interconnected with PVB interlayers. The last ALON (closest to the leeward side) is connected to a polycarbonate layer using an IonP interlayer. The individual ALON and sapphire layers are each 3.0 mm thick and the polycarbonate layer is 4.5 mm thick. Each IonP layer is 1.5 mm thick, unless state otherwise. The overall thickness of the section is 42.0 mm. FIG. 18 a shows the makeup of the section.

Two numerically induced variations were investigated to establish the performance of the modified TIRS section with respect to the .50 caliber, Armor Piercing, M2 round.

Variation 1

The 46-g (709.5-grains) .50 caliber ammunition is used. The results are shown in FIGS. 18 a-18 d. FIG. 18 b shows the final (rest) configuration of the slug formed during the event. The position of the slug does not vary beyond the 240 ms time-mark as shown in FIGS. 18 c and 18 d by the vertical position and velocity outputs, respectively, of the stations along the axis of symmetry of the projectile. The final depth of rest is 2.68 cm into the TIRS section. The confidence is 98% that the ammunition will not penetrate the TIRS arrangement.

Variation 2

The 52-g (800-grain) .50 caliber ammunition is used. The results are shown in FIGS. 19 a-19 d. FIG. 19 a shows the final (rest) configuration of the slug formed during the event. The position of the slug does not vary beyond the 260 ms time-mark as shown in FIGS. 19 b and 19 d by the vertical position and velocity outputs, respectively, of the stations along the axis of symmetry of the projectile. The K.E. of the impacting bullet dissipates within the first 200 ms and its velocity within the first 260 ms of impact. The final depth of penetration of the tip of the slug is at 4.05 cm which is very close to the 4.2 cm total thickness of the composite section. The center of gravity of the slug formed, however, is at 3.0 cm or less than 72% of the total thickness of the TIRS. As shown by FIG. 19 a spall occurs during this event. The spall velocity, however, is very low (order of 10-15 m/s) and, thus, the potential for major injury or death is minimal. The confidence is 85% that the ammunition will not penetrate the TIRS arrangement.

Example 4

The results from this example are summarized in Table 1. The table represents a matrix of results obtained from the simulation of various levels of ballistic threats as dictated by the UL-752 standard. In particular, Levels I through X are shown herewith. In all cases, the maximum (upper) value of the velocity range dictated by the UL-752 ballistic standard is used.

Table 1 shows the minimum thickness required to defeat each of these levels of ballistic threat, as well as their respective areal densities. The velocities, masses, and description of the individual threats are reported for the sake of completeness. Table 2 shows the through-the-thickness distribution for each of the layers used in constructing the composite sections. In addition to the individual layer (ply) thicknesses shown, the uncertainty in thickness for each of these layers is included.

The areal densities and thicknesses required by the new composite section are favorably compared to commercially available typical laminated glass sections that can defeat the first four UL-752 Levels. The latter, as reported in the literature (R1), are 31.75, 38.1, 44.5, and 50.8 mm for Levels I through IV, respectively.

A visual summary of the UL-752, Level IX, is shown in FIGS. 20 a-20 d. The initial and final (rest) configurations of the .30-caliber, 10.8-g ammunition, with an initial impact velocity of 910 m/s are shown in FIGS. 20 a and 20 b, respectively. The velocity variation of select points along the ammunition's vertical axis (axis normal to the impacting surface) is shown in FIG. 20 c. It can be seen that the slug formed is arrested within the first 150 ms from impact, despite the fact that its K.E. is brought to zero within 85 ms, as indicated in FIG. 20 d. This is due to the fact that the combination of the “fused” target and bullet is still in motion beyond 85 ms but within the first 150 ms from impact.

FIGS. 21 a-21 d show the equivalent results for the .50-caliber, 46-g ammunition, with an initial velocity of 942 m/s, corresponding to the upper bound of the UL-752, Level X ballistic standard. In this case, the velocity of the slug formed reaches a stationary state after 275 ms, as shown in FIG. 21 c. The slug's K.E., as seen in FIG. 21 d, dissipates before the 235-ms time mark. This is due to the fact that the combined slug and target body formed after impact is still in motion between the 235-ms and the 275-ms time marks.

In all cases, the methodology used in the derivation of the different materials and section thicknesses employ the use of numerical methods which explicitly model the individual constituent thicknesses in conjunction with an optimization module. The latter takes into consideration a combination of state variables, as well as the overall section and individual ply thicknesses. It is an iterative methodology that yields a new cross-section that is optimized with respect to weight and ply distribution in the through-the-thickness direction with the aim of defeating each of the UL-752, Levels I-X ballistic standards.

Example 5

The importance of an alternate reinforced interlayer section is addressed in this example. The interface layer consists of a polymeric material, such as PVB or IonP, and it is reinforced with single-crystal layers of ALON, a few micrometers thick. The purpose of the reinforcing crystal found in the interlayer is to produce a more efficient energy absorption and redirection mechanism. The reinforcing crystals act as waveguides that divert the energy due to impact from the through-the-thickness direction to the in-plane direction. Alternate substitutes to the ALON reinforcement of the interlayer, are single-crystal layers of aluminum oxide, or single-crystal layers of any other spinels, or any other single crystal layers of other high hardness compounds. The optical quality of the interlayer section is affected by the nature of the reinforcing crystals.

A reinforced interlayer with a single crystal acting as a waveguide to redirect impact energy can be applied to a variety of laminated materials that include an interlayer and where increased strength and impact absorption is desirable.

Uses and Investigations

Some additional capabilities investigated are listed below:

-   -   1. The composite section can be converted into a section with         variable or reduced light transmissivity. The ballistic         performance of the original section will not be affected.     -   2. The thermal conductivity of the TIRS sections can be enhanced         and yield a reduced U-value suitable for “green” energy         applications by inducing minor modifications to the original         composite section. The ballistic performance of the original         section will not be affected. By substituting one of the plies         with a different semi-transparent material (including spinels or         any other photochromic material) the overall thickness that         offers the same level of protection will not be altered.     -   3. The thermal conductivity of the TIRS section can be enhanced         by introducing thermochromic material in one or more of the         interlayers connecting the constituent plies. The ballistic         properties of the section will remain unaffected. The light         transmissivity will be reduced.     -   4. The current composite section can be altered to become a         photovoltaic (PV) section without compromising its ballistic         capability. Inclusion of one or more semitransparent         photovoltaic thin-film(s) is necessary. All the PV types can be         integrated within the interfacing layers of a current TIRS         section. It is anticipated that only a single, thin-film PV will         yield equivalent translucent sections as that of the original         TIRS sections. Various degrees of transparency are possible         depending on the application of the composite section. The         ultimate purpose of this portion of the investigation is to         provide ballistic protection and, at the same time, use PV cells         to produce electricity.     -   5. A weighted approach of importance for each of the additional         characteristics (ballistic resistance, transparency, thermal         conductivity, thickness, weight, cost of manufacture and others)         is to be incorporated in the analysis and design of any new TIRS         section.     -   6. The overall size of the TIRS can be expanded by incorporating         different types of connection techniques/systems. Some of these         include, but are not limited to, (a) typical glass curtain wall         connectors (usually metal connectors), (b) gasket type of         connectors that allow for partial rotation of the different TIRS         units comprising the structure, (c) continuous joint connections         that can be of different degree of transparency, etc.     -   7. Smart glass technologies can be easily incorporated into the         interlayer of the proposed composite, allowing the control of         light and thereby heat transmission.

REFERENCES

-   R1— “Security Design Guide for Solutia Laminated Architectural     Glazing,” Saflex Company, 08810/SOL, 2007.

TABLE 1 Characteristics of Composite Sections Required to Defeat UL-752 Ballistic Levels Ammo UL-752 Characteristics Target Characteristics Confidence Standard Ammunition Mass Velocity Areal Density Thickness PerCent Level Description Shots (g) (m/s) (kg/m{circumflex over ( )}2) (mm) (%) I 9 mm 2, 3 8.00 394 17.94 6.95 97 II .357 Magnum 2, 3 10.20 419 19.51 7.51 97 III .44 Magnum 2, 3 15.60 453 29.91 12.10 97 IV .30 Caliber 1 11.70 852 51.98 21.50 98 V 7.62 mm 1 9.70 922 51.96 21.40 98 VI 9 mm 5 8.00 430 20.62 7.52 96 VII 5.56 mm 5 3.56 1033 44.16 17.60 96 VIII 7.62 mm 5 9.70 922 51.96 21.40 95 IX .30 Caliber 1 10.80 910 52.85 21.80 97 X .50 Caliber 1 46.00 942 82.98 35.00 97 VII* 5.56 mm 5 3.56 1310 46.67 18.50 91 *Modified UL 752 Level VII Standard w/ 30% Velocity

TABLE 2 Individual Layer and Overall Section Thicknesses Required to Defeat the UL-752 Ballistic Threats for Levels I through X Target Thickness UL-752 Ply Standard Ammunition Thickness Overall Thickness Level Description Material (cm) (cm) I 9 mm ALON 0.300 ± .002 0.300 Interlayer 0.150 ± .001 0.450 Sapphire 0.245 ± .002 0.695 II .357 Magnum ALON 0.300 ± .002 0.300 Interlayer 0.150 ± .001 0.450 Sapphire 0.301 ± .002 0.751 III .44 Magnum ALON 0.300 ± .002 0.300 Interlayer 0.150 ± .001 0.450 Sapphire 0.300 ± .002 0.750 Interlayer 0.150 ± .001 0.900 ALON 0.310 ± .002 1.210 IV .30 Caliber ALON 0.300 ± .002 Interlayer 0.150 ± .001 Sapphire 0.300 ± .002 Interlayer 0.150 ± .001 ALON 0.350 ± .002 1.250 Interlayer 0.150 ± .001 Sapphire 0.300 ± .002 Interlayer 0.150 ± .001 ALON 0.300 ± .002 2.150 V 7.62 mm ALON 0.300 ± .002 Interlayer 0.150 ± .001 Sapphire 0.300 ± .002 Interlayer 0.150 ± .001 ALON 0.350 ± .002 1.250 Interlayer 0.150 ± .001 Sapphire 0.300 ± .002 Interlayer 0.150 ± .001 ALON 0.290 ± .002 2.140 VI 9 mm ALON 0.300 ± .002 0.300 Interlayer 0.150 ± .001 0.450 Sapphire 0.302 ± .002 0.752 VII 5.56 mm ALON 0.300 ± .002 Interlayer 0.150 ± .001 Sapphire 0.300 ± .002 Interlayer 0.150 ± .001 ALON 0.350 ± .002 1.250 Interlayer 0.150 ± .001 Sapphire 0.360 ± .002 1.760 VIII 7.62 mm ALON 0.300 ± .002 Interlayer 0.150 ± .001 Sapphire 0.300 ± .002 Interlayer 0.150 ± .001 ALON 0.350 ± .002 1.250 Interlayer 0.150 ± .001 Sapphire 0.300 ± .002 Interlayer 0.150 ± .001 ALON 0.290 ± .002 2.140 IX .30 Caliber ALON 0.300 ± .002 Interlayer 0.150 ± .001 Sapphire 0.300 ± .002 Interlayer 0.150 ± .001 ALON 0.350 ± .002 1.250 Interlayer 0.150 ± .001 Sapphire 0.300 ± .002 Interlayer 0.150 ± .001 ALON 0.330 ± .002 2.180 X .50 Caliber ALON 0.300 ± .002 Interlayer 0.150 ± .001 Sapphire 0.300 ± .002 Interlayer 0.150 ± .001 ALON 0.300 ± .002 1.200 Interlayer 0.150 ± .001 Sapphire 0.300 ± .002 Interlayer 0.150 ± .001 ALON 0.300 ± .002 Interlayer 0.150 ± .001 2.250 Sapphire 0.300 ± .002 Interlayer 0.150 ± .001 ALON 0.300 ± .002 Interlayer 0.150 ± .001 Sapphire 0.500 ± .003 3.500 

1. A transparent impact resistant system, comprising: at least one sheet of aluminum oxynitride; at least one sheet of single-crystal aluminum oxide; and at least one interlayer attached between the at least one sheet of aluminum oxynitride and the at least one sheet of single-crystal aluminum oxide.
 2. The transparent laminate of claim 1, wherein the interlayer comprises an energy absorption layer.
 3. The transparent impact resistant system of claim 2, wherein the interlayer further comprises a reinforcement layer.
 4. The transparent impact resistant system of claim 2, wherein the interlayer further comprises a waveguide.
 5. The transparent impact resistant system of claim 4, wherein the waveguide comprises a spinel element.
 6. The transparent impact resistant system of claim 4, wherein the waveguide comprises a single sheet of aluminum oxynitride.
 7. The transparent impact resistant system of claim 4, wherein the waveguide comprises a single sheet of single-crystal aluminum oxide.
 8. The transparent impact resistant system of claim 1, wherein the interlayer comprises polyvinyl butyral.
 9. The transparent impact resistant system of claim 1, wherein the interlayer comprises a polymer.
 10. The transparent impact resistant system of claim 9, wherein the polymer layer comprises an ionoplast layer.
 11. The transparent impact resistant system of claim 1, wherein the at least one sheet of aluminum oxynitride is positioned on the side of a potential impact relative to the at least one sheet of single-crystal aluminum oxide.
 12. A transparent impact resistant system, comprising: a first rigid layer; a second rigid layer; and at least one interlayer attached between the first rigid layer and the second rigid layer, wherein the interlayer comprises an energy absorption layer and a waveguide.
 13. The transparent impact resistant system of claim 12, wherein the waveguide comprises a spinel element.
 14. The transparent impact resistant system of claim 12, wherein the waveguide comprises a single sheet of aluminum oxynitride.
 15. The transparent impact resistant system of claim 12, wherein the waveguide comprises a single sheet of single-crystal aluminum oxide.
 16. The transparent impact resistant system of claim 12, wherein the energy absorption layer comprises polyvinyl butyral.
 17. The transparent impact resistant system of claim 12, wherein the energy absorption layer comprises a polymer.
 18. The transparent impact resistant system of claim 12, wherein the first rigid layer comprises at least one sheet of aluminum oxynitride positioned on a side of a potential impact.
 19. The transparent impact resistant system of claim 12, wherein the second rigid layer comprises at least one sheet of single-crystal aluminum oxide.
 20. A transparent impact resistant system, comprising: a first rigid layer; a second rigid layer; and at least one interlayer attached between the first rigid layer and the second rigid layer, wherein the interlayer comprises an energy absorption layer and a reinforcement layer.
 21. The transparent impact resistant system of claim 20, wherein the first rigid layer comprises a first spinel element and the second rigid layer comprises a second spinel element.
 22. The transparent impact resistant system of claim 20, wherein a thickness of the reinforcement layer is less than 0.05% of a thickness of the interlayer.
 23. The transparent impact resistant system of claim 20, wherein the reinforcement layer comprises a spinel element. 